Leibniz - The Principle of
Sufficient Reason
Harry Swan
Philosophy 203
2/15/11
Perceptions in the Simple
Substance
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Leibniz asserts that variability in the simple
substance (monads) comes from the fact that it can
have perceptions.
This is how he explains thought at the most basic
level; he rejects the idea that thought can be
explained in terms of moving parts, like other
phenomena.
These are our sensory perceptions, which we retain
in the form of “sense memory”, the same way that
animals do.
Leibniz calls them truths of fact.
Reasoning vs. Fact
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What separates us from animals is our mind, or our
capacity to reason, which gives us knowledge of
“eternal and necessary truths” (M 29).
He calls these “truths of reasoning”, as opposed to
those of fact.
“The truths of reasoning are necessary and their
opposite is impossible. The truths of facts are
contingent, and their opposite is possible.” (M 33)
Reasoning - “2 + 3 = 5.”
Fact - “There is snow on the ground.”
Leibniz will show how both are necessarily true.
Two Great Principles
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There are two principles we use to determine truth.
Principle of Contradiction: If something involves a
contradiction, it is false. If something contradicts the
false, it is true.
“2 + 3 = 6” contains a contradiction, “2 + 3 = 5”
contradicts that and does not contain a
contradiction in itself.
Principle of Sufficient Reason: Nothing can be true
without a sufficient reason for it to be true and not
false.
We must find a cause (sufficient reason) for the
truth to be true.
Necessary Truths
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These reasons and contradictions are often not
readily apparent, we must analyze and find them.
“When a truth is necessary, its reason can be found
by analysis, resoling it into simpler ideas and
simpler truths until we reach the primitives” (M 33).
For truths of reasoning, the analysis is finite.
When we analyze “2 + 3 = 6” to mean “5 = 6”, the
contradiction is apparent.
This is how we arrive at mathematical and logical
truths.
Truths of Fact
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“But there must also be a sufficient reason in
contingent truths, or truths of fact, that is…where the
resolution into particular reasons could proceed into
unlimited detail because of the division of bodies
into infinity” (M 36).
“There is snow on the ground” is true because we
can give a sufficient reason for the presence of snow
on the ground, but we are then compelled to give a
sufficient reason for that, and so on into infinite
analysis…
God is the Sufficient
Reason
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“And this is why the ultimate reason of things must
be in a necessary substance in which the diversity of
changes is only eminent, as in its source. This is
what we call God” (M 38).
This substance (God) is the source of everything;
there is nothing outside of it and it is absolutely
perfect, because it contains all possible reality.
All things are derived from it, and get their limited
perfections from it.
An absolutely perfect being would not act without
sufficient reason, so there is a sufficient reason for
the existence of things, and truths of fact.
Questions
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What do we think of this? Is this a valid account of
truth?
Is this a convincing argument for the existence of
God? Could we nowadays substitute God for the Big
Bang?
How does this affect free will/determinism?